Summary
Intracellular chloride activities, (Cl) c , and the electrical potential difference across the mucosal membrane, ψmc, were determined in the isolated small intestine of the winter flounder, using Cl-selective and conventional (KCl-filled) microelectrodes. In the presence of a Na-containing buffer ψmc averages −69mV and (Cl) c averages 24mM, a value that is 3.4 times that predicted for an equilibrium distribution across the mucosal membrane. On the other hand, when the tissue is then perfused with Na-free buffer, (Cl) c slowly falls to a value that does not differ significantly from that predicted for an equilibrium distribution, and ψmc depolarizes significantly. Finally, when the tissue is again bathed in the Na-containing buffer, (Cl) c rapidly returns to a value well above equilibrium.
These results, together with those of Frizzellet al. (J. Membrane Biol. 46:27, 1979), provide direct evidence that: (1) Cl is accumulated against its electrochemical potential difference (32mV) by this tissue, and (2) this accumulation is coupled to and energized by the entry of Na down its steep electrochemical potential difference.
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Duffey, M.E., Thompson, S.M., Frizzell, R.A. et al. Intracellular chloride activities and active chloride absorption in the intestinal epithelium of the winter flounder. J. Membrain Biol. 50, 331–341 (1979). https://doi.org/10.1007/BF01868896
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DOI: https://doi.org/10.1007/BF01868896